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Low-temperature sintering(LTS) experiments of UO2 pellets and their results were reported. Moreover, a routine process of LTS for UO2 pellets was primarily established. Being sintered at 1 400 ℃ for 3 h in a partially-oxidative atmosphere, the relative density of the pellet can be up to around 94%. Pellets with such a high density are of benefit for following-up reduction-sintering processes. Orthogonal test indicates that the importance of factors affecting the density decreases in the sequence of partial-oxidative sintering temperature and time, reduction-sintering time and temperature, and sintering atmosphere. It is found that it is helpful to introducing a small amount of water vapor into the sintering atmosphere during the latter stage. It is believed that it is the key factor to raise the O/U ratio of original powder in order to improve the properties of the low-temperature sintered pellets. 相似文献
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烧结工艺对超细WC-6%Co-0.6%(VC/Cr_3C_2/TaC)硬质合金性能的影响 总被引:1,自引:1,他引:0
硬质合金的性能随烧结工艺的不同而会发生变化,本文在1 380℃,经真空烧结和压力烧结(4 MPa)制备超细WC-6%Co-0.6%(VC/Cr3C2/TaC)(质量分数)硬质合金,分别采用SEM分析、XRD检测、钴磁检测、矫顽磁力检测、洛氏硬度检测、抗弯强度检测等方法,对比研究了真空烧结和压力烧结对合金显微组织和力学性能的影响。结果表明:与真空烧结相比,压力烧结提高了合金的相对密度,降低了孔隙度,从而提高了合金的综合性能。本次实验中,压力烧结条件下制备的合金相对密度为99.4%,孔隙度为A02B00,硬度为93.8 HRA,TRS为1 830 MPa。 相似文献
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烧结助剂对Salon常压烧结的影响 总被引:3,自引:0,他引:3
研究了以Y2O3和Y2O3+La2O3为烧结助剂的Sialon陶瓷的常烧结过程及其相结构。结果表明:添加6%Y2O3在1750℃常压烧结1h可获得相对密度大于99%的Sialon陶瓷;La2O3可部分或大部分取代Y2O3,混合烧结助剂的最佳烧结温度(1800℃)略高于单纯以Y2O3为烧结助剂的最佳烧结温度(1750℃)。加入La抑制了α′相和YAG相的生成,选择合适的工艺条件,可制得α′ β′复相陶瓷。探讨了用Col-Gel化学法混料替机械法混料的可能性,由于γ-Al2O3转变成α-Al2O3等原因,化学混料法的效果不如机械法。 相似文献
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用掺碳活化烧结技术制取碳化硼材料 总被引:4,自引:1,他引:3
研究了 3种烧结活化剂 (葡萄糖、酚醛树脂和硬脂酸 )和不同的掺碳量对碳化硼烧结的影响。发现活化剂葡萄糖优于其它两种活化剂 ,以葡萄糖为活化剂 ,掺碳 3%,在 2 2 70℃氢气中常压烧结 1h获得的碳化硼材料密度为 2 .0 6 g/cm3 (相对密度 82 %) ,这一密度高于文献中报道的采用相同粒度粉末制得的结果。 相似文献
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掺碳碳化硼活化烧结及其动力学 总被引:12,自引:2,他引:10
研究了在中位径为0.42μm的碳化硼微粉中添加1%~4%碳为活化剂的烧结过程。研究了烧结坯的密度、抗弯强度、晶粒度与掺碳量、烧结温度、保温时间的关系。在一定烧结温度以上,少量碳的掺入明显提高了烧结活性,烧结坯密度明显提高,在本实验条件下最佳掺碳量为1%~2%,最佳烧结温度为2160~2200℃。研究了掺碳碳化硼烧结动力学,得出其物质迁移机制主要为晶界扩攻。最后研究了其相组成,掺入的碳除溶解于碳化硼 相似文献
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利用放电等离子烧结炉在不同温度下对SiC陶瓷进行烧结,烧结温度分别为1250、1450、1650、1850℃,升温速度均为200℃/min,升到温度后立即冷却。基于烧结后SiC陶瓷的扫描电镜观察,对SiC陶瓷的放电等离子烧结机理进行了初步探讨。研究结果表明,随着烧结温度的提高,SiC陶瓷的致密化程度逐渐提高,在1250℃和1450℃烧结的试样微观组织中很难发现烧结现象,但在小颗粒间发生局部的烧结痕迹,在1650℃烧结的试样微观组织中存在小颗粒的烧结现象,大颗粒间仍然没有烧结,颗粒形貌基本保持原始粉末的形貌,而在1850℃烧结的试样微观组织中存在大量的烧结颈现象,而且颗粒形貌呈球形。因而SiC陶瓷的放电等离子烧结机理可能是低温下的焦耳热烧结机理和高温下的放电和焦耳热共同作用机理。 相似文献
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Je-ha SHON Jong-moon PARK Kyeong-sik CHO Jae-keun HONG Nho-kwang PARK Myung-hoon OH 《中国有色金属学会会刊》2014
Effects of various sintering methods such as spark plasma sintering (SPS), hot pressing (HP) and electric resistance sintering (ERS) on the microstructure and mechanical properties of commercial pure titanium (CP-Ti) powder consolidations with particle size of <147 μm, <74 μm and <43 μm were studied. The smaller particle powders are densified to proceed at a higher rate. Dense titanium with relative density up to 99% is found to take place at 850 °C under 30 MPa of SPS and HP condition. However, in case of ERS, CP-Ti powders were densified almost at 950 °C under 30 MPa. The microstructure of sintered titanium is composed of equiaxed grains at 850–950 °C. The yield strength of sintered body composed of <43 μm powder is 858 MPa by using SPS at 850 °C under 30 MPa. When there is a higher content of small particle, the higher yield strength value is obtained both by using SPS and HP. However, when ERS is introduced, the highest yield strength is 441 MPa at 950 °C under 30 MPa, which shows much lower values than those by SPS and HP methods. ERS method takes much less sintering time compared with SPS and HP. Nevertheless, higher sintering temperature results in lower strength and elongation because of brittle fracture. 相似文献
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在非均相沉淀法制备的Fe-Mo包覆Si3N4金属陶瓷粉末中添加助剂MgO-Y2O3进行常压烧结,采用X线衍射仪(XRD)、电子能谱(EDS)、电镜扫描(SEM)等方法研究了不同烧结温度下该金属陶瓷相组成和显微结构等方面的演化趋势。结果表明:温度升高有利于金属相的转变和液相的生成,在复合粉末还原过程中,Si3N4的强还原性将Mo、Fe依次直接还原出来并反应生成Fe3Mo化合物,随着还原温度的升高,该金属间化合物与Si3N4反应生成Fe3Mo3N;同时Mg、Y氧化物与基体反应生成的MgSiO3、Fe17Y2加速了Fe3Mo3N的形成。1 600℃烧结时,Fe3Mo3N仍能稳定存在,但在1 700℃烧结时发生分解,材料组织中出现大量长径比较高的晶须状物质生成,同时表面粘附一层小颗粒物质.烧结温度为1 750℃时,金属小颗粒相仍得以保留,材料基体中晶须状物质消失。 相似文献
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TiB2陶瓷活化烧结及制备技术 总被引:1,自引:1,他引:1
TiB2材料具有高熔点、高硬度、耐磨、耐腐蚀、抗氧化以及导电性好和导热性好等优点,是一种具有广泛应用前景的新型陶瓷材料。但是其极强的共价键晶体结构和较低的自扩散系数,使得其很难获得致密的陶瓷材料。主要从添加助烧剂和烧结技术两方而介绍了TiB2陶瓷活化烧结方法的研究进展,并分析了该技术促进材料烧结致密化的机制,同时介绍了热压烧结和放电等离子(SPS)烧结技术。 相似文献
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Pulse electric current sintering (PECS) was tried for Ir-25 at.% Nb (Ir3Nb), which has a high melting temperature of about 2435 °C. Ingot powder was made by crashing an ingot, and the ingot powders
were sintered at temperatures between 1700 and 1900 °C up to 2 h under 40 MPa. Pure-metal powder was mixed to achieve a composition
of Ir-25 at.% Nb, and the pure-metal powders were sintered at a temperature between 1700 and 1900 °C for up to 1 h. The microstructure
and phase structures of sintered samples were investigated by scanning electron microscopy (SEM) and x-ray diffractometry.
The sintering mechanism and problems for Ir3Nb in PECS are discussed. 相似文献
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钨具有高密度、高熔点、低的热膨胀系数、优异的导电导热性能以及良好的耐腐蚀性能,在许多领域得到了广泛的应用,但由于熔点高,钨的烧结致密化困难。活化烧结是制备高密度和高性能钨及其合金材料的重要方法,其中添加镍元素是钨粉活化烧结最重要的手段之一。本研究从镍的活化效果、掺杂含量以及活化机理方面综述了镍对钨的活化烧结作用,并提出了添加金属元素的钨粉活化烧结的研究方向。 相似文献
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Hot-pressed sintering was employed to prepare the sodium super ionic conductor (Na1+xZr2SixP3-xO12,1.8≤x≤2.2)ceramics and compare with the sample obtained from normal-press sintering. The phase formation, density, and conductivity of the hot-press sintered and the normal-press sintered samples were investigated in detail. Results show that the density of NASICON ceramics and the degree of crystallization can be improved by hot-press process efficiently. The density of the sample sintered by normal sintering is obviously lower than that sintered by hot press. XRD analysis indicates all the hot press sintered samples contain mainly monoclinic NASICON and no ZrO2 phase was found. The ionic conductivity of normal-press sintered sample is much lower than that of hot-press sintered sample. When the composition is close to Na3Zr2Si2PO12 , the dc conductivities of the hot press sintered samples were in the order of 10-3 S·cm-1.The variation of the ac conductivity with frequency in the high frequency region agrees with the power law feature of σ(ω) ∝ωn(0<n<1). 相似文献